1. Field of the Invention
The present invention relates to a device which improves the lift and decreases the drag of a sail by the provision of a thick profile instead of a simple flat surface held up by a fixed mast. Contrary to the conventional sail, this thick profile will be able to be controlled on demand and independently of the ambient wind.
2. Description of the Prior Art
Conventional simple surface sails lead to an accumulation of aerodynamic perturbations (the drag of the mast disturbing the laminar flow, important induced drag leading to a bad sharpness ratio, etc.) and, in addition, they cannot be correctly controlled for the following reasons:
1. The sail should be as flat as possible, when the wind rises; but because of the wind this sail is hollowed, so that considerable forces must be applied in order to prevent this deformation.
2. The sail should be hollowed when the wind slackens; but this soft wind has insufficient force to hollow this thin profile.
At the present time, several types of thick propulsive systems or thick sails are known as follows:
The suction effect in the cylinder designed by the Cousteau Institution which is an important improvement of the discoveries made by Mr. MALAVARD, based on the Magnus principle of the rotatable cylinder.
The thick propeller of Messrs. PHILLIPPE and COESSIN.
The rigid sail used on the oil coaster "Shin Aito Kumaru" invented in Japan.
In spite of their obvious advantages, these different discoveries have some defects, such as overweight in the high parts, complex and fragile systems requiring either a large staff or computer assistance, the absence of the hauling down facility, use of the least power possible for their carrying out their functions, and, on the other hand, they are often far from the idea of a sail which normal consumers perceive, from the points of view of aesthetics and price, but especially from the need for using cordages and other rigging, as in the conventional sail.